A spin-injection magnetic random access memory (MRAM) which uses a perpendicular magnetization film as a recording layer is excellent for reducing a write current and achieving a large capacity. A stacked film of Cobalt (Co) having a dense atomic plane and Platinum (Pt) has a magnetocrystalline anisotropy as high as 107 erg/cm2 and has such a low resistance as to achieve a high magnetoresistance ratio (MR ratio). Therefore, the stacked film is notable as a technology for putting a large capacity MRAM to practical use.
Meanwhile, ruthenium (Ru) is used as a buffer for a CoPt alloy from a viewpoint of crystal matching. However, the Ru buffer increases a damping constant of a recording layer, and therefore involves a problem of a large writing current. In a spin-injection MRAM using a perpendicular magnetization film, a write current is proportional to the damping constant and inversely proportional to a spin polarizability, and increases in proportional to a square of an area size. Therefore, reduction of the damping constant, increase of the spin polarizability, and reduction of an area size are mandatory technologies to reduce the write current.